Composition and process for whitening fibers



COMPOSITION AND PROCESS FOR WHCITENIN FIBERS Allan Gilbert Osborne, Pen'cader Hundred, Del., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Filed Sept. 25, 1957, Ser. No. 686,003

6 Claims. (Cl. 252-417) This invention relates to a novel process for whitening textile fibers such as cotton or hydrophobic textile fibers,

by using a novel class of fluorescent whitening agents.

It is an object of this invention to provide a novel process as aforesaid, which will be applicable generally to textile fibers, including cotton and hydrophobic fibers such as nylon, cellulose acetate, polyester fiber, etc. It is a further object to provide a process as aforesaid which will result in a bleach-fast whitening effect. A still further object is to, provide a process as aforesaid which is characterized by simplicity of application and high economy of materials. achievements of this invention will become apparent as the description proceeds.

' The art of whitening or brightening textile fiber and paper is based on the observation that fibrous materials which normally have a dull, yellowish cast when in the white, unbleached state, become whiter and brighter if treated with agents which fluoresce under ultraviolet light. Presumably the action of the ultraviolet rays present in ordinary daylight is sufficient to excite these agents upon the fiber to emit fluorescence which overcomes the undesirable tinge of color in the unbleached fiber. Best results are obtained when the shade of fluorescence is complementary to that of the unbleached fiber, so that the colors will cancel out each other. Since the most common off-white shade of unbleached cellulosic and nylon fibers is yellowish, the most desirable shade in a fluorescent is blue.

Another very important demand developed by the trade is bleach fastness. Inasmuch as the aforementioned fluorescent agents are generally incorporated into soap and synthetic detergents, which are packaged and marketed for household use, and inasmuch as in household practice laundered articles are often subjected to bleaching with various agents, for instance hypochlorites, it is essential that the fluorescent transferred from the detergent to the fiber shall not be removed or destroyed by the action of bleach.

In addition to the above two primary qualifications, an agent for the purposes of this invention should be capable of being synthesized economically from readily available materials, and should have suflicient fluorescent power (often referred to as tinctorial strength) to give the desired effect at a minimum cost. It should also have affinity for both cellulose and hydrophobic fiber and should be capable of being dissolved or readily dispersed in water in the concentrations that would normally be used in the treatment of therespective fibers.

Now I find that the above objects and aims of the process are satisfied to a remarkable degree by employing as whitening agents a class of compounds not hitherto suggested for this purpose. More particularly, the class of compounds applicable according to this invention may be defined by the general formula Additional objects and aten ' cooled. The product is collected on a filter, washed s or Patented Apr. 18, 1961 (I. Am. Chem. Soc. 67, 1318), who synthesized them by condensing terephthalaldehyde with 2- or 4-picoline, respectively.

The various lower-alkyl substitution derivatives set forth in the examples hereinbelow appear to be new compounds and may be synthesized by analogous methods.

That these compounds would be suitable for the purpose of this invention was not to be foreseen, considering the combination of practical requirements which a commercial whitening agent must satisfy, to wit, correct shade of fluorescence, good aflinity for the fiber being treated, versatility as to the fibers to which it is applicable, and good bleach fastness. It may be noted, for instance, that I have tested other compounds having the sequence phenylCH:CH-pyridyl and found some of them utterly useless for the purpose of this invention because of lack of aflinity for cellulosic fiber.

The mode of applying my novel agents to the fiber may follow established general practice in this field. Thus, my novel agents may be dispersed in water to produce a dye bath containing from 0.001 to 0.5 part of the whitening agent (by weight) for each parts of fabric to be treated; the fabric to be whitened may then be impregnated with this bath, squeezed and dried. Or my novel agents may be incorporated into soap or synthetic detergents, in proportion of 0.01 to 0.5% by Weight. Particularly suitable for this purpose are the commercial soaps and synthetic detergents which are marketed in flake or powder form for household use. When such treated cleansers are used by the housewife for laundering, the whitening agent automatically goes into the fiber.

Without limiting this invention the following examples are given to illustrate my preferred mode of operation. Parts mentioned are by weight.

PART I.PREPARATION OF THE AGENTS A. 134 parts (1 mole) of terephthalaldehyde, 279 parts (3 moles) of u-picoline and 306 parts (3 moles) of acetic anhydride are dissolved in 630 parts of 1,2,4- trichlorobenzene and then are heated at reflux (about C.) for about 72 hours. The reaction mixture is with 200 parts of ethanol, and dried. The yield of 2,2-(p-phenylenedivinylene)dipyridine is 210 parts (75% of theoretical) melting at 226 to 228 C.

In a similar manner the following additional compounds have been prepared by me from the initial materials indicated. The melting points are those of the products.

B. 2,2 (2,5 dimethyl p phenylene-divinylene)- dipyridine; from 2,5-dimethyl-terephthalaldehyde and a-picoline; M.P.=194196 C.

C. 4,4-(p-phenylenedivinylene)dipyridine; from terephthalaldehyde and y-picoline; M.P.=236240 C.

D. 5,5 diethyl 2,2 (p phenylenedivinylene)- dipyridine; from terephthalaldehyde and 5-ethyl-a-pico line (2-methyl-5-ethyl-pyridine); M.P.=2092l2 C.

PART II.APPLICATION TO FIBER Abbreviations used: o.w.f.=on weight of the fiber; r.f.i.=relative fluorescence intensity.

3 Example 1 Cotton cloth is washed with a 0.4% by weight aqueous solutionof a heavy duty detergent containing 0.01%

(o.w.'f.) of 2,2-(p-phenylenedivinylene)dipyridine for 25 minutes at 130 F. The fabric is removed from the bath, rinsed with distilled water and dried.

The cloth so' treated is considerably whiter than untreated cloth when examined visually by skilled textile technicians and when tested quantitatively using a Beckman DU spectrophotometer with reflectance attachment. The treated cotton cloth exhibits a 35% to 40% r.f.i. whereas the untreated cloth shows 2% to r.f.i.

The heavy'duty detergent referred to above may be any commercial detergent for instance, a product whose active ingredient is a long-chain alkyl aryl sulfonate or a long-chain alcohol sulfate.

' Similar results are obtained, if in lieu of the agent above named one uses in this procedure the products named under B, C and D in Part I, above.

Example 2 When nylon cloth is substituted for the cotton cloth mentioned in Example 1, similar results are obtained. The r.f.i. of the treated fabric ranges from 29% to 38% with the four agents named, whereas the untreated cloth has an r.f.i. of 2 to 5%.

Example 3 When the procedure of Example 1 is applied to acetate rayon fabric, essentially similar results are obtained. The r.f.i. of the treated fabric ranges from 20 to 25% (for the 4 agents named), whereas the untreated fabric has an r.f.i. of 2 to 5%.

Example 4 Example 5 TEST FOR BLEACH FASTNESS An aqueous solution of detergent and the novel whitening agent was preparedaccording to the details given in Example 1, except that sodium hypochlorite was added in quantity calculated to yield a concentration of 0.02% of available chlorine (based on bath weight). utes later, cotton cloth was entered into the dye bath and the temperature of the mixture was maintained at 130 F. for 25 minutes. The cloth was removed from the bath, rinsed with cold distilled water, and dried. The cloth thus treated, when measured by the spectroscopic method described in Example 1, was found to have 80 to 100% of the fluorescence produced on a control sample of cloth treated under the same conditions in a similar bath but containing no bleach.

Tests for light-fastness, substantivity and wash-fastness were also carried out, and showed my novel compounds to compare favorably in respect to these qualities with the best fluorescents which are now on the market.

Example 6 Following the procedure of Example 1, the four agents named in Part I were tested again on cotton, nylon and cellulose acetate but at a bath concentration of 0.002% o.w.f. The resulting r.f.i. ranged from 10 to 23% on cotton, 13 to 18% on nylon, and 8 to 9% on cellulose acetate.

For comparison, it is mentioned here that of presentday commercial fluorescents hardly any are applicable to all these three fibres with good results. Thus, 2-sulfo-4- naphthotriazolyl-stilbene gives satisfactory results on cot- Two minton and nylon, but exhibits no afiEinity for cellulose acetate. 7-(N,N-dimethylamino)-4-methy1coumarin is satisfactory on nylon and cellulose acetate, but has no atfmity for cotton.

When my novel whitening agents are incorporated into textile detergents (by which term I mean both soap and synthetic detergents), their mode of addition may be suited to practical convenience. Thus, in the case of soap, the addition may be done at any suitable stage in its manufacture, for instance the final stage in the soap kettle, or during the crutching or milling of the soap.

In the case of synthetic detergents the addition may, likewise, be performed at any stage in their manufacture or isolation. (See for instance, U.S.P. 2,702,278.) As instances of suitable synthetic detergents may be mentioned the sodium fatty alcohol sulfates such as sodium lauryl sulfate, hydroxy ethyl sulfonic' acid andsarcosine condensation compounds of fatty acid radicals having 8 carbon atoms or more, such as the condensation product of oleyl chloride with the sodium salt of isethionic acid;

. amides of various types, such as the condensation product of oleyl chloride with the sodium salt of taurine, and alkali metal alkyl aryl sulfonates. A more elaborate list of such synthetic detergents may be found in U.S.P. 2,643,197, col. 7, and in U.S.P. 2,702,278, col. 2.

The commercial form of the textile detergent may contain other customary additives such as builders, perfumes, antioxidants, etc. 'In such cases, the percentages above indicated for the added whitening agent are preferably based on the entire weight of the commercial product.

My novel whitening agents may also be incorporated into laundry starches, softening agents, bluings or any other commercial compositions which are intended for use on the fiber or which come in contact with the fiber at one stage or another during the laundering process.

The advantages of this invention will now be readily apparent.

Fluorescent whitening agents of the subject invention impart to textile fibers a bluish-white fluorescence which is outstanding when viewed under ultraviolet light. The light-fastness of these agents is comparable to that of the best fluorescents which are now on the market. Fabrics treated with the agents of this invention appear whiter and brighterthan the corresponding untreated fabric. Fibers treated with the agents described herein retain fluorescence even after treatment with hypochlorite or peroxide bleach. The most important advantage of these fluorescent whiten- 7 ing agents is their substantivity on many types of textile fibers coupled with their excellent resistance to bleach. Since they are substantive on cotton and hydrophobic fibers, such as nylon, cellulose acetate and polyester fiber, they may be used to whiten fabrics made up of mixtures of these fibers. In this respect, the whitening agents of this invention are notably superior to the best fluorescents which are now on the market.

I claim as my invention:

1. The process of whitening textile fiber, which comprises impregnating the same with an aqueous bath containing a compound of the formula wherein the Rs represent pyridyl radicals of the group consisting of 2-pyridyl, 4-pyridyl and their alkyl substitution derivatives having from 1 to 4 C-atoms in the alkyl radical, while X and Y stand each for a member of the group consisting of hydrogen and alkyl radicals having 1 to 4 C-atoms, said compound being present in said aqueous bath in a quantity equal to from 0.001 to 0.5 part by weight of said compound for each parts by Weight of the fiber to be treated.

2. The process of whitening textile fiber, which comprises laundering the same with a synthetic, organic, textile detergent containing a compound as defined in assumes 5 claim 1 to the extent 0.01 to 0.5% by weight, based on the gross weight of said textile detergent.

3. The process of whitening textile fiber, which comprises laundering the same with a Water-soluble detergent soap containing a compound as defined in claim 1 to the extent 0.01 to 0.5% by weight, based on the gross weight of said textile detergent.

4. A laundering composition comprising a synthetic,

organic, textile detergent and a compound as defined in claim 1, the amount of the latter being from 0.01 to 0.5% by weight based on the weight of said laundering composition.

5. A laundering composition comprising a textile detergent and a compound as defined in claim 1, the amount of the latter being from 0.01 to 0.5% by weight based on 1;,

the weight of said laundering composition, and said textile detergent being a member of the group consisting of soap, long-chain alkyl sulfates and long-chain alkyl aryl sulfonates.

6. A laundering composition comprising a Water-soluble detergent soap and a compound as defined in claim 1, the amount of the latter being from 0.01 to 0.5% by weight based on the weight of said laundering composition.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Stearns et al.: Soap and Sanitary Chemicals, March Blout et al.: J. Amer. Chem. Soc., vol. 67, pp. 1315- 1319 (1945). 

1. THE PROCESS OF WHITENING TEXTILE FIBER, WHICH COMPRISES IMPREGNATING THE SAME WITH AN AQUEOUS BATH CONTAINING A COMPOUND OF THE FORMULA 